Structural Influencing Factors on Zn II /Cd II Coordination Polymers Based on Tri‐pyridyl‐bis‐amide: Assembly, Structures, Fluorescent Sensing and Selective Photocatalysis

Fourteen new Zn II /Cd II coordination polymers tuned by semi‐rigid “V”‐like tri‐pyridyl‐bis‐amide ligands with different spacers and different dicarboxylates co‐ligands, namely, {[Zn(L1)(mip)] · H 2 O} n ( 1 ), {[Zn 2 (L1) 2 (hip) 2 ] · H 2 O} n ( 2 ), {[Zn(L1)(oba)] · H 2 O} n ( 3 ), {[Zn(L1)(chda)] · H 2 O} n ( 4 ), {[Cd 2 (L1)(mip) 2 (H 2 O)] · 2H 2 O} n ( 5 ), {[Cd(L1)(hip)] · 4H 2 O} n ( 6 ), {[Cd(L1)(oba)] · H 2 O} n ( 7 ), {[Cd 3 (L1)(chda) 3 ] · 4H 2 O} n ( 8 ), [Zn(L2)(mip)] n ( 1a ), {[Zn(L2)(hip)(H 2 O)] · 3H 2 O} n ( 2a ), [Zn(L2)(oba)] n ( 3a ), {[Cd(L2)(hip)] · 3H 2 O} n ( 6a ), {[Cd(L2)(oba)] · H 2 O} n ( 7a ), [Cd(L2)(chda)] n ( 8a ), [L1 = N , N′ ‐di(pyridin‐3‐yl)pyridine‐2,6‐dicarboxamide, L2 = N , N′ ‐di(pyridin‐3‐yl)pyridine‐3,5‐dicarboxamide, H 2 mip = 5‐methylisophthalic acid, H 2 hip = 5‐hydroxyisophthalic acid, H 2 oba = 4,4′‐oxybis(benzoic acid), H 2 chda = trans ‐1,4‐cyclohexanedicarboxylic acid] have been hydrothermally synthesized and structurally characterized. Complexes 1 – 4 based on the same L1 ligand and Zn II ion show various structures. Complex 1 features a two‐dimensional (2D) network, which consists of a linear [Zn‐mip] n chain and [Zn‐L1] n left‐, right‐handed helixes. Complex 2 is a twofold interpenetrating 2D→2D network. In complex 3 , Zn 2 (L1) 2 loops were connected by oba anions creating a 1D channel‐like structure. Complex 4 is a 2D layer containing [Zn‐chda] n right‐handed helixs and Zn 2 (L1) 2 loops. Complexes 5 – 8 with Cd II ion exhibit different structures. Complex 5 features a 1D belt structure based on Cd 4 (COO) 4 subunits. However, complex 6 exhibits a 2D network constructed from [Cd‐hip] n ladder‐like chains and Cd 2 (L1) 2 loops. Complex 7 shows a 1D double chain structure containing [Cd‐oba] n zigzag chain and [Cd‐L1] n meso ‐right‐handed helix. Complex 8 exhibits a 2D network based on 2D [Cd‐chda] layer and 1D [Cd‐L1] n meso ‐helical chain. For complexes 1a – 8a based on L2 ligand, complex 1a is a 2D layer containing [Zn‐mip] n linear chain and [Zn‐L2] n meso ‐helical chain. The structure of complex 2a is very similar to that of 3 . Complex 3a exhibits a 2D grid network containing 1D [Zn‐oba] n and [Zn‐L2] n chains. Complex 6a shows a 2D layer based on [Cd 2 (hip) 2 ] n double chain and [Cd‐L2] n chain. The structure of complex 7a is very similar to that of 7 . Complex 8a is a 3,5‐connected 3D framework with the Schläfli symbol of (4 2 .6 5 .8 3 )(4 2 .6), which is constructed from [Cd‐L2] n channel‐like chains and chda linkers. The structural diversity of the title complexes indicates that the tri‐pyridyl‐bis‐amide ligands with different spacers, the dicarboxylates and central metals play important roles in tuning the dimensionalities and structures of the target complexes. The title complexes exhibit excellent photocatalytic activity and selectivity for organic dyes degradation under UV light. In addition, fluorescent sensing behaviors of 3 , 6 , 7 and 7a toward different organic solvents have been investigated in detail.